The present invention relates to a copier, facsimile apparatus, printer or similar image forming apparatus and, more particularly, to a developing device of the type having a developing roller facing an image carrier via an opening formed in a casing, and a pair of seal members provided on the casing and adjoining opposite side edges of the opening for preventing a developer from being scattered around.
The problem with a developing device of the type described is that during development a developer is scattered around via opposite side edges of the opening of the casing since a developing roller facing a photoconductive drum or similar image carrier cannot strongly retain the developer at opposite ends thereof. To eliminate this problem, it is a common practice to attach seal members to the casing in such a manner as to cover the opposite side edges of the opening. The seal members may be implemented as sheets of polyurethane or similar substance or as elastic members of foam urethane.
However, the seal members in the form of sheets has a drawback that when the amount of developer deposited on the developing roller increases, the resulting magnet brush is apt to get on the seal members and be scattered around via the clearance between the seal members and the drum. Moreover, the carrier particles contained in the developer is spun off due to the rotation of the developing roller and directly scattered to the outside. Such carrier particles are also scattered around via the clearance between the drum and the lower portion of the casing. By contrast, the seal members made of an elastic material prevent the magnet brush from getting thereon and also prevents the carrier particles spun off from being directly scattered to the outside since no clearances exist between the seal members and the drum. However, the carrier particles spun off impinge on and rebound from the elastic seal members. This part of the carrier particles is scattered around via the clearance between the drum and the lower portion of the casing without returning to the magnet brush.
Further, a copier, facsimile apparatus, printer or similar machine is apt to incline in the axial direction of a developing roller thereof due to the location where it is installed. Then, despite the seal members, the developer is likely to leak at the lower side of the developing device with respect to the inclination of the machine. Hence, the margin available with the conventional developing device in respect of inclination is limited.